The reasons behind the development and outcomes of peace negotiations remain a subject of debate among scholars and practitioners. Structural conflict conditions of the conflict are often emphasized as key explanatory variables. However, this approach often neglects the actual intricacies of peace talks once they are in place and, instead, correlates negotiation outcomes with variables that are not actively part of them. Drawing on conflict resolution theory and the theory of complexity, the article proposes a theory for understanding the dynamics of peace negotiations. The main argument is that in a complex environment like one of peace talks, decisions on process design can be a key determinant of the effort devoted by the parties, and thus, of the negotiations unfolding. One contribution of this approach is the recognition of the potential of a negotiation to transform the relationship between the parties from one of conflict to one of cooperation in a joint effort to work toward a negotiated solution, provided that the complexity of the negotiation and the uncertainties associated to it are properly managed. Negotiation process design can provide some of the tools to do so. Similarly, this approach makes it possible to understand the existence of negotiations in which the parties are interested in keeping the dialogue open, regardless of some conditions of the conflict, for instance, alleged lack of ripeness. As an example, the paper studies the case of the Colombian government's parallel peace negotiations with the FARC and the ELN in the period 2010–2018, which shows the possible role of process design variables in the different paths of these two negotiations.